In recent years, the method of contactlessly supplying electrical energy to wireless power receivers in a wireless manner has been used instead of the traditional method of supplying electrical energy in a wired manner. The wireless power receiver receiving energy in a wireless manner may be directly driven by the received wireless power, or a battery may be charged by using the received wireless power, then allowing the wireless power receiver to be driven by the charged power.
For allowing smooth wireless power transfer between a wireless power transmitter which transmits power in a wireless manner and a wireless power receiver which receives power in a wireless manner, the standardization for a technology related to the wireless power transfer is undergoing.
As part of the standardization for the wireless power transfer technology, the Wireless Power Consortium (WPC) which manages technologies for a magnetic inductive wireless power transfer has published a standard document “System description Wireless Power Transfer, Volume 1, Low Power, Part 1: Interface Definition, Version 1.00 Release Candidate 1 (RC1)” for interoperability in the wireless power transfer on Apr. 12, 2010.
On the other hand, Power Matters Alliance as another technology standardization consortium has been established on March 2012, developed a product line of interface standards, and published a standard document based on an inductive coupling technology for providing inductive and resonant power.
A wireless charging method using electromagnetic induction is frequently encountered in our lives, and for example, wireless charging method using electromagnetic induction is utilized by being commercialized in electric toothbrushes, wireless coffee ports and the like.
In recent years, in addition to a method of transmitting wireless power in a one-to-one manner in the related art, a method of allowing one wireless power transmitter to transmit power to a plurality of wireless power receivers has been developed.
Though a wireless power transmitter changes an operating frequency or operating voltage of wireless power to control power in the related art, it causes a problem in controlling power for each wireless power receiver when transmitting power to a plurality of wireless power receiver at the same time.
Accordingly, the present disclosure proposes a method of controlling power in a wireless power receiver and a method of controlling power using a variable capacitor.